1. Field of the Invention
The invention pertains to the machining of rotating workpieces by the use of broaching tools sequentially brought into engagement with the workpiece for removing metal therefrom.
2. Description of the Related Art
It is known to mount a plurality of workpieces on a moving chain and move the workpieces past a fixed tool such as shown in U.S. Pat. Nos. 2,088,119 and 2,191,193. Further, it is known to mount a tool upon a moving chain, such as in a power chain saw, and attention is directed to U.S. Pat. Nos. 1,244,789 and 2,523,301.
However, the advantages of mounting a plurality of tools in such a manner as to permit the tools to be sequentially moved past a rotating workpiece in order to permit rapid metal removal from the workpiece and yet accurately control such removal and sizing of the workpiece has not been previously appreciated. It is this concept of the linear movement of broach type workpieces past a rotating workpiece with which the invention deals.
An object of the invention is to provide a broach machine tool system for use with a rotating workpiece wherein a high rate of production can be achieved at a high level of accuracy.
Another object of the invention is to provide a broach type machine tool for removing metal from a rotating workpiece wherein the tool moves in a linear path while engaging the workpiece.
A further object of the invention is to provide a broach type machine tool capable of removing metal from a rotating workpiece wherein a plurality of broach type tools are mounted upon a chain in a spaced manner wherein workpieces may be loaded and unloaded from supporting spindles intermediate machining operations.
In the practice of the invention, the linear broach machine includes a frame having spaced opposed rotating spindles defining a workpiece axis of rotation. One or both of the spindles can be powered by a controlled drive unit, and each of the spindles includes clamping mechanism whereby the workpiece may be accurately supported at each end. The machine of the invention was created particularly for heavy duty turning, such as turning the main bearings for internal combustion engine crankshafts. However, it will be appreciated that the invention may be utilized in any turning operation and is particularly suitable in those situations where it is desired to remove a considerable amount of metal in a relatively short time under high conditions of accuracy and tool life.
In the preferred embodiment of the invention, a combination of sprockets are located in a triangular relationship whereby the tool carriers may be mounted upon spaced parallel chains guided by the sprockets wherein the carriers will move through a triangular path. It is possible to only use two combinations of chain sprockets in the broad concept of the invention, but the use of three combinations of sprockets permits a greater length of chain to be used permitting a greater number of tool carriers to be mounted upon the chain, thereby providing increased flexibility of tool carrier spacing and the rate of chain movement.
Two of the chain sprocket combinations are spaced in such a relationship as to cause the tool carriers mounted upon the chains to move in a path of movement transverse, normally perpendicular, to the axis of workpiece rotation. In this manner, broaching tools mounted upon the tool carriers will move past the workpiece in a tangential manner. Preferably, the two chain sprocket combinations positioning the tool carriers during a cutting action are vertically spaced wherein the tool carriers and tools are moving in a downward direction during cutting.
Usually, two or more broaching turning tools are mounted upon a tool carrier, each subsequent tool being located closer to the axis of workpiece rotation wherein the last cutting tool will produce the finished diameter. With some turning operations, the broaching and turning tools necessary to make an entire cut may be located on adjacent tool carriers if it is necessary that three or four tools are required for a machining operation.
The tool carriers may be spaced along the chain as desired, and usually, sufficient spacing will exist between the carriers necessary to perform a workpiece operation, and the rate of tool carrier movement is such, that after turning, the workpiece spindles may be stopped, the finished workpiece removed from its supporting spindles, and a new workpiece mounted upon the spindles such that the next series of tools will engage the new workpiece and the turning cycle repeated with a new set of tools without stopping the tool carriage movement. The chain mounting of the tool carriers and tools permits a high rate of production with minimal wear upon any given tool, and turning machines constructed in accord with the invention are capable of high production turning operations for extended periods of time between tool replacement.
To ensure accuracy, the tool carriers are held upon a rigid bedway mounted on the machine frame during cutting. The tool carriers include guide surfaces firmly held against bedway guide surfaces (bearings) and as the bedway is well lubricated, it is possible to support the tool carriers on the bedway during cutting in a relatively movable relationship and yet hold the necessary tolerances to achieve accurate tool removal without chattering.
It will be appreciated that the aforedescribed machine meets all of the objects of the invention as set forth above.